who knows the difference in rpm of 30 pitch p5x andt 29 6 blade herring

Should be close. The Hydro may be slightly higher in rpm. The boat makes a big impact.

Depends upon the diameter of the Hering and the drive heigth.

Julie

100 / 200 rpm+ or -

as well the rpm's will differ across the board. low rpm, cruise, top speed, etc,,,,. either prop will run around 9% slip close to surfacing.